This obsolete spelling uses a digraph including the letter ㅅ to represent the tensing of the other consonant, a phenomenon now represented with doubled consonants. For instance, modern 꿈(kkum) was written ᄭᅮᆷ(kkum). This spelling, called the 된시옷 (doensiot) or "tense s" spelling, was the most common way to write tense consonants until at least around 1900. The "tense s" spelling continued to be common into the early twentieth century until it was deprecated in the major spelling reforms of the 1930s.
This particular form, etymologically spurious, is first attested in the late seventeenth century and gradually displaced the etymologically accurate ㅶ (from Middle Koreanㅶ(pc-)) over the course of the next century (Lee and Ramsey 2011, p. 135).
